1. Field of the Invention
The present invention relates to a digital demodulating apparatus, in particular, including means for controlling the power to be supplied; and also to a digital receiver, a controlling method of the apparatus, a computer program product, and a recording medium recording thereon the product.
2. Description of Related Art
In a digital demodulating apparatus, when the power is supplied to each circuit component constituting the apparatus, the magnitude of the power necessary for accurate demodulation processing varies in accordance with the signal reception condition. In general, on the assumption that the reception condition is the worst, a magnitude of power having a certain margin is supplied. However, when the reception condition is good, there is no necessity of supplying such a high power. Therefore, in order to reduce the power consumption, it is thinkable that the power to be supplied to each circuit component is controlled in accordance with the signal reception condition.
For example, Japanese Patent Unexamined Publication No. 2005-109912 discloses an apparatus that controls the power to be supplied while judging the signal reception condition. The apparatus includes an error correcting unit for correcting errors in a signal, and detects the error rate in the error correcting unit. When the apparatus judges on the basis of the detected error rate the reception condition to be good, the apparatus reduces the power to be supplied to its high frequency section. Thereby, the power consumption can be reduced. In this case, even when the reception sensitivity of the high frequency section is lowered due to the reduction in the power supplied to the section, the good reception condition can be kept while the error rate is not more than a reference value. On the other hand, when the error rate is more than the reference value, the apparatus judges the reception condition to be bad, and stops the reduction in the power to be supplied to the high frequency section. Thereby, the reception sensitivity of the high frequency section is intended to be improved so as to ensure a good reception condition.
However, there is a case that conditions for controlling the power do not correspond to the degree of the variation in the reception condition. For example, when the control conditions do not correspond to the variation in the reception condition, there is possibility that a power control operation is performed even though the variation in the reception condition is gentle and the reception condition merely temporarily varies. In this case, the power to be supplied may be increased as soon as the reception condition temporarily varies. This reduces the efficiency of the power control as a whole. In addition, when the reception condition frequently varies, there is possibility that the power control properly following the variation can not be ensured. Thus, the apparatus disclosed in the above publication has possibility that the power control can not properly be performed in accordance with the variation in the signal reception condition.